DENVER 
The expected nomination of Democratic U.S. Sen. Ken Salazar to President-elect Barack Obama's Cabinet could set off a series of political dominoes in Colorado, with leading contenders to replace him including Denver's mayor and Salazar's brother, U.S. Rep. John Salazar.

Ken Salazar has been chosen by Obama as interior secretary, an official familiar with the selection of Obama's Cabinet said Monday. The official spoke on condition of anonymity, saying the official was not authorized to disclose any personnel decisions not yet announced.

Democratic Gov. Bill Ritter said he has bittersweet feelings about the prospect of choosing a replacement for Salazar. He cited Salazar's experience as head of the state Department of Natural Resources under former Gov. Roy Romer, and his Western roots.

"Ken Salazar has been an extremely effective United States senator for Colorado these past four years, particularly as a moderate and as a centrist," Ritter said in a statement.

"But if a nomination to join the Obama administration comes to pass, Sen. Salazar would make an equally outstanding Interior secretary for the country, for the West and for Colorado.

Political consultant Floyd Ciruli said it would be difficult, but not impossible, for Ritter to appoint Salazar's brother John to fill a vacant Senate seat. The appointee would serve until the next general election in 2010 and would be required to run then if he or she still want the job.

Ciruli said John Salazar doesn't have the statewide support his brother garnered during his term as state attorney general and could have a tough time against a Republican challenger. John Salazar was elected in the 3rd Congressional District largely because of name recognition and the millions of dollars Democrats spent to get Ken Salazar elected, Ciruli said.

John Hickenlooper, Denver's quirky mayor who won office with a campaign promising to chop down parking meters, may have a better chance, Ciruli speculated.

He said Hickenlooper continually out-polls other prominent Colorado Democrats, including Ritter and Ken Salazar.

Another possible replacement on Ciruli's list: House Speaker Andrew Romanoff, who is term-limited and is leaving office in January. Romanoff is currently a finalist for Colorado secretary of state. The incumbent, Republican Mike Coffman, was elected to replace retiring U.S. Rep. Tom Tancredo in the 6th Congressional District.

Ciruli said that in Ken Salazar, Senate Democrats would lose a valuable lawmaker known for seeking bipartisan support – but that he could be even more valuable to Colorado and the region as interior secretary.

Democratic U.S. Rep. Diana DeGette has received several calls encouraging her to seek an appointment to fill Salazar's seat, said her spokesman, Kristofer Eisenla.

"It's definitely something she is going to have to consider," he said.